Nut Cracker

ABSTRACT

The present invention relates to a device and a method for increasing the yield, as well as for enabling an increase in productivity and an increased amount of production, and at the same time to improve purification of process water and waste water, respectively by decreasing the waste water flow and the amount of pollutants in the waste water.

TECHNICAL FIELD

The present invention relates to a device and a method for increasingthe yield (getting more final product from a given incoming amount ofraw materials and additives), as well as for enabling an increase inproductivity (amount per time unit) and an increased amount ofproduction (amount of production per given amount of pollutant to an endrecipient), and at the same time to improve purification of processwater and waste water, respectively, by decreasing the waste water flowand the amount of pollutants in the waste water. The method comprisesincreased recycling (recovery, closing) of process water, in combinationwith utilization of substances to be included as materials in an endproduct formed, instead of constituting pollutants in the waste. At thesame time, equivalent or improved dewatering properties are achieved inthe production process, thereby enabling increased productivity and/oramount of end product formed, in relation to the maximum amount ofeffluent to the recipient allowed for the activity.

These effects are achieved by introducing, in or between any one orseveral of the water processing steps of the entire production, a newstep based on an effect that can be achieved by certain strong oxidizingagents, preferably ozone. The method means hereby that the oxidizingagent functions both as a type of ionizer (polarizer) of, as well as atype of catalyst for polarization between, particles, substances andadditives suspended in the water. The effect is influenced by factorssuch as the concentration of oxidizing agent, the degree ofinstallation, position and order of water flows in the process, mixingmethods, suspension characteristics of pollutants, choice and propertiesof chemical additives (retention agents, etc.), dosage of additives anddosing positions, as well as other parameters. Hence, the said effectgoes beyond prevailing and common effects that can be achieved by strongoxidizing agents and that are used, to a limited degree, in this type ofindustry in order among other things to kill microbiological cultures,to decompose pollutants comprising COD and BOD, to bleach substances inthe end product, etc., as is known from FI 110683B, e.g.

The method results in an economical gain, by decreasing the discharge ofsubstances (pollutants) in the waste water, instead to be recycled tothe process as raw materials, and by enabling an increased productivityand/or production capacity by improved dewatering properties for the webof material formed during production.

BACKGROUND

The following background and description focuse on process water in pulpand paper industries, but the invention is not limited to the fields ofapplication used to exemplify the technique and its use. The techniqueis applicable on other types of process industries having substancespresent in the process water.

Large amounts of water are used in the production processes of pulp andpaper industries. It is an objective for this sector of the industryamong other things to reduce the amount of pollutants discharged, aswell as the amount of water discharged (waste water), also meaning thatthe amount of externally added fresh water is reduced. There is a striveto achieve this by increasing the amount substances used in theproduction, which substances would otherwise be released in the form ofpollutants in order thereafter to be made subject for furtherpurification, decomposition and final depositing in the environment.

This objective arises by a) gradually increased requirements,established by the authorities and relating to amounts of pollutanteffluents allowed from the process industries, as well as b) the needfor the industry constantly to try to increase productivity andprofitability by increasing the utilisation of added raw materials,decreasing the amount of cost-increasing additives, and by trying toincrease production.

The demands on decreasing of effluents are constantly raised, both as aconsequence of common and constant technical improvements, but also inorder to encourage new technical improvements with the aim ofenvironmental control and a decreased environmental impact. Therefore,it is an important and central issue to the line of business to developnew methods for decrease of effluents and for improvement ofprofitability, whenever compatible.

As such, decreased effluents give the possibility to increase productionwithin allowed/authorized effluent limits. Nowadays, various types ofenvironmental certificates are awarded if you are below stipulatedlimits, which may result in marketing benefits.

The industry strives to accomplish so called closed systems in theproduction process, concerning internal process water, which means thatefforts are made to re-use (recycle) most possible of the process water,thereby to minimize the amount of waste water and of course consequentlyalso the amount of added fresh water. In this context, waste water meansmaterial-containing (polluted) process water that is led to an externalpurification plant outside the process plant, and thereafter, afterprocessing, to the recipient.

The quality of recycled process water tends always to be graduallyimpaired at increased “closing” or re-use (degree of recycling) in theplant/mill. In turn, this leads to a gradual quality impairing effect,both on the actual production process and on the product produced in theplant/mill. This is a central problem.

External waste water purification takes place by a combination ofchemical, physical and biological purification methods. It is of utmostimportance to minimize the amount of pollutants in the waste water aswell as the amount of waste water, in order to minimize investment andoperational costs for a purification plant.

Generally, it can be said that water treatment and water purificationwithin pulp and paper industry comprises three separate steps or parts.The first part is cleaning and treatment of incoming raw water for theplant. Generally, such water is taken from a lake or a large stream.

The second part comprises purification of the internal process water,and the third part comprises purification of polluted water that is notintended to be re-used (closed) in the process and that therefore is ledaway therefrom as final waste water.

Generally, this means that the second step takes place within the plantand that the third step takes place outside the plant, in a dedicatedwaste water purification plant. The measures for the second steppurification (within the plant) could partly be of the same basictechnical nature as the measures undertaken in the third step, but couldalso be of totally different nature.

The pollutants in the form of suspended substances and acid-consumingsubstances, leaving the production process by the waste water, consistto a major part of raw material substances such as cellulose materialand additives. These substances would have given an increased productionyield if they could have been better kept and utilised as a part of theend product instead of leaving the plant by the waste water.

Internal measures to decrease effluents in the form of waste water forexternal purification include modifications of the production processes,in order to generate less effluents, as well as various methods forrecycling internal process water (so called white water) used in theplant, in order to recycle raw materials in such water to the producedend product.

One example of internal purification of water for recycling, ispurification of internal process water around a paper machine. Paperproduction requires a lot of water, since the stock (water plus fibreplus additives, etc.) must be much diluted before it is lead onto thepaper machine wire. Thereafter, the water is drained, partly on the wire(the strainer screen on which the paper is formed), and partly in thepress section of the paper machine. This drainage water is loaded withcellulose material and other suspended materials, as well as dissolvedorganic and inorganic substances.

Fresh water is constantly supplied to the process water system (whichalso means that roughly the same amount of water leaves the system inthe form of waste water). The major part of the process water isrecycled to the paper machine. This closing decreases water consumptionand loss of raw materials.

It is mainly the possibility of effective separation of substances inthe process water that limits the degree of recycling of the processwater. At poor separation of substances from the process water, or at anincreased degree of recycling, accumulation of materials take place inthe process water, and this may lead to problems in the form offormation of slime, clogging, as well as impaired production and productqualities.

Usually, flocculants are charged to increase retention of materials inthe formed product. It is important in this case that the flocculationresults in flocks of material with beneficial dewatering properties,since the dewatering is of decisive importance to the productivity of apaper machine.

Today, purification of the internal process water to be recycled usuallytakes place in screens, filters, settling basins and flotation plants.

Purification techniques of today, of waste water from the plant, inexternal purification plants, are based on a combination of mechanical,chemical and biological purification steps. By biological purification(biopuriflcation) is meant the use of cultures of micro-organisms inorder to decompose pollutants and acid-consuming materials, otherbacterial cultures, etc.

It is also known in a few pulp and paper mills to use ozone in the last(external) purification step, after extensive biological treatment. Inthese cases, ozone is above all used in large amounts to oxidizehigh-molecular materials, being very hard to decompose in a biologicalpurification plant, into substances of lower molecular size that canthereafter be decomposed in a subsequent biological purification step.

It is important to avoid large variations in the load of the externalpurification plant, since this has to be dimensioned for a maximum load,and since variations will, as such, result in disturbances in theexternal purification process.

It should be mentioned that by techniques of today, purification stepsoutside the production in the actual plant/mill, constitute aneconomical load on the total result for the pulp and/or paperproduction.

In some applications, ozone is also used to kill bacteria, see FI110683B e.g. In this application, a method is described of using ozoneto kill micro-organisms in the internal process water in paper mill.

There is a constant need for improved purification techniques in themills, and the need increases concurrently with a gradually increasedenvironmental consciousness in terms of more stringent rules foreffluents allowed from the mills. Of special interest are techniquesalso having the possibility to improve purification of process waterwithin the mill (within the production process), and that allow forincreased recycling of process water at maintained quality for theproduction process and for formed products, and thereby decreasedrequirement of fresh water supply and decreased waste water discharge.

If the technique moreover can be formed such that material separatedfrom the process water in the purification steps can be recovered as amarketable product, i.e. be completely or partly recycled in theproduction process, instead of, as now, constituting a load on theexternal waste water purification, then an economically profitableincentive has been introduced for a gradual improvement of thepurification technique. A cost has been converted into “profitable”recovery, as well as increased productivity, i.e. a purification thatpays its own cost or even more.

Accordingly, there is a need for new technique that improves theproduction economy (profitability) of the mills, thereby ensuringfulfilment of stipulated outlet limits, and also ensuring qualitydemands for the production and its product, by fulfilling at leastone/some, preferably all of the following criteria:

a decreasing the amount of waste waterb decreasing the need for incoming raw water (fresh water)c decreasing the need of or the cost for depositingd recovering of useful/valuable substances from recycling and wastewater, respectivelye decreasing loss of raw materials (otherwise leaving as pollutants inthe effluents)f allowing for increased productivity.

BRIEF DESCRIPTION

The present application relates to the accomplishment of chemicallyaffecting the substances in the process water, thereby becoming morereactive in order to accumulate to form larger aggregates, so calledflocculation, and also so that the substances will more easily reactwith chemicals added to improve flocculation, the now said beingachieved by mixing in an oxidizing agent such as ozone gas in theprocess water. In the present invention, an oxidizing agent such asozone is used for a different purpose than what has been done previouslyin the process line. The oxidizing agent may be ozone or some otheroxidizing agent having an potential of oxidation of preferably above 1.5V.

By adding an oxidizing agent such as ozone integrated with the process,several advantageous effects are achieved.

As mentioned above, ozone has been used previously in externalpurification in order to improve separation of COD. Ozone has also beenused as a bactericide in the internal process water, and as a bleachingagent. In the present application, ozone is used to achieve aflocculation, or to render it more effective, of substances in the flowof fibre pulp as well as in the process water. By adding ozone as closeas possible to the forming step (the effect will be better the moreclose to the forming step that the ozone is added), a larger amount ofthe substances will be caught in the network of cellulose, i.e. in theproduct, and thereby materials are recovered from the process water,which materials would otherwise be lost as pollutants, also resulting inthe white water becoming cleaner, such that a larger part of the whitewater can be recycled in the short and long circulations. Besides this,combinatory advantages are attained in that also the bactericidalproperties of the oxidizing agent can be used. Moreover, by using thebleaching properties of the oxidizing agent, a possibility is achievedto change the colour of excessive sludge, thus enabling this to be mixedinto the raw material pulp, without affecting the colour of the endproduct.

The result thereof is a decrease in the amount of substances that leavethe production by the waste water, which means an increased yield inrelation to used raw material, as well as a decreased load on theexternal purification plant, resulting in an economical contribution tothe pulp and/or paper mill, instead of becoming a costly problem ofdepositing.

The process water quality is also generally improved by addition ofoxidizing agents, preferably ozone, thus enabling decreased waterconsumption for the production process for paper and pulp (increasingthe degree of recycling, i.e. increasing the degree of closing).Bacteria and bacteria growth is reduced, otherwise leading to odour,formation of slime and disturbances in substance flocculation.

The improved flocculation properties that can be achieved by addition ofoxidizing agents, will also result in an improved function (increaseddegree of separation) for the mechanical equipment for treatment ofprocess water, such as screens, filters and similar. At the same time,the function is also improved for settling and flotation equipment,intended for separation of materials from the process water. Inparticular, it is fragments of cellulose fibres and other particulatesubstances that in this way are more efficiently separated from theprocess water.

The flocculation of substances and the process of forming fibre materialinto a fibre network, in all steps of the production processes withinpulp and paper industry, is of central importance to the productionresult. The addition of an oxidizing agent will give a beneficialstructure of the fibre network during forming of the network thusincreasing retention of substances in the network, and at the same time,separation of water from the fibre network is facilitated due to thechanged network structure. Thereby, utilisation of the material isimproved (increased retention), as well as so called runnability (lessfrequent disturbances during production) for the various process stepsin pulp and paper production.

By the measures above, i.e. the oxidation treatment of the processwater, there will be a decrease in the amount of pollutants constitutinga load on the external waste water purification. Still however, someexcessive sludge will be formed in the external purification step. Sincethe treatment with an oxidizing agent is bactericidal, besides being acatalyst for aggregation of the substances, a recycling to the (paper)production process can take place by oxidation treatment of this sludgematerial. The effect will be bacteria-reduction in the sludge andaggregation of the substances, to be caught by the production process,in which it is screened out with the product.

The treatment with the oxidizing agent is also colour-reducing,resulting in that the most often darker colour of the sludge can bereduced to a suitable nuance, as desired.

A higher dosage of the oxidizing agent will be more colour-reducing thana lower dosage. This affects the possibility to recycle the sludge as apart of the products, without affecting the colour of the material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic drawing of material and water flows in pulp andpaper production, in which an ionization and oxidation step 12 has beenintroduced in the process,

FIG. 2 shows an embodiment example of the mixing-in of ozone gasaccording to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described in detail, with reference to thedrawings.

FIG. 1 shows a schematic drawing of material and water flows in pulp andpaper production, in which an ionization and oxidation equipment 12 hasbeen introduced in the process, preferably just before the formingequipment 14. Raw materials 1 and water 2 are supplied to the productionprocess 3. The product 5 is produced and water vapour 4 and pollutedoutput process water 6 leaved the production process 3. The outputprocess water 6 is purified in an external purification plant 7 forwaste water, from which one part leaves as sludge 8 for deposit and/orincineration, and the purified water 9 is let out to the recipient (i.e.the environments). Looking closer into the production process 3, it canbe seen that raw material 1 and water 2 are supplied to a pulp and stockpreparer 10. Also recycled process water 15, 20 is supplied to the pulpand stock preparer, from the storage tank 19 for white/process water andthe forming equipment 14 (preferably a paper machine), respectively. Thepulp/water mixture 11 resulting form the pulp and stock preparer 10, isthereafter exposed to an ionization and oxidation step 12 (see FIG. 2).The ionized and oxidized output water 13 from the ionization andoxidation equipment 12 is thereafter introduced in the forming equipment14. Preferably, the water flow 11, 13 is also treated with retentionagents. In the production line, the distance between the pulp and stockpreparer 10 and the forming equipment 14 can be relatively large. It ispreferred that the ionization and oxidation equipment 12 is situatedmore or less in direct connection with the forming equipment 14. Theforming equipment 14 produces the paper product 5 by distributing thetreated, fibre-carrying water 13 (the pulp suspension) onto a formingwire. A part 15 of the white water 15, 16 from the forming equipment 14is recycled directly to the pulp and stock preparer 10, in the so calledshort circulation, another part 16 goes to internal purificationequipment 17. Furthermore, water also leaves as water vapour 4 that islet out. The internal purification equipment 17 may for example containvarious screening steps and/or flotation steps, in which a part 18 ofthe water can be re-used and therefore be sent to a storage tank 19 inorder to be recycled to the pulp and stock preparer 10. The water 6 thatcontains a higher concentration of reject material than water 16 and 18,and that is not led to the storage tank for process water 19, is sent toexternal purification equipment 7 (such as flotation basins) thatseparates bio-sludge 8 and water 9 that is considered to be adequatelypurified and that is therefore returned to the environments. Undercertain circumstances, parts of the bio-sludge 8 can be returned to theproduction process 3 at the ionization and oxidation equipment 12.

One embodiment example of the mixing-in of ozone is shown in FIG. 2,i.e. the ionization and oxidation equipment 12 that is inserted betweenthe pulp and stock preparer 10 and the forming equipment 14 (see FIG.1). A pulp/water mixture 11, typically having a pulp concentration ofbetween 0.5 and 5%, is pumped into a container 27 (the mixture isnormally diluted with internal process water that in turn contains pulpconcentrations of normally below 0.5%). Ozone gas 24 is added to thebottom of the container 27, by being injected into the container 27 inthe form of small bubbles 25, in order thereby to increase contactsurfaces against the pulp/water mixture 11. The ozone gas 24 can begenerated by using an ozone generator. Preferably, a stirrer 23 ispositioned inside the container 27, in order to stir the pulp/watermixture 11 and further to increase the possibilities for the ozone gasbubbles 25 to react with the substances in the pulp/water mixture 11.Appropriately, other stirring means for the pulp/water mixture 11, canbe used. The top of the container 27 is provided with outlet pipes 21,22 for remaining ozone gas 24 that has passed the pulp/water mixture 11without having reacted. The remaining ozone gas 24 can either be led viapipe 21 to an ozone-destroyer, or it can be returned to the ozonegenerator via pipe 22, for re-use in order thereafter to be recycled tothe container 27.

In order to achieve a result that is as good as possible, it ispreferred for the ozone gas 24 to have a long contact time with theprocess water. Therefore, the ozone gas 24 is preferably added in theabove described reactor vessel 27. However, it can also be added in alonger pipe in which the ozone gas 24 is mixed with the pulp mixture 11.Preferably, the process water 11 should be stirred during the reactiontime. The dwell time for the liquid 11 in vessel 27 is a function of thevolume of the vessel 27 and the liquid volume flow through vessel 27. Ifthe concentration of ozone is high in the ozone gas 24, the contact timemay be shorter in order to achieve the same effect of the ozone gas (theso called Ct factor, where gas concentration and reaction time is aproduct factor that weighs the importance of changes in gasconcentration and reaction time, respectively). Stirring can take placeeither by a stirrer 23 in a container 27, or by a so called static mixerin a pipe through which process water 11 and ozone gas mixture 24 arepumped. A combination of a container 27 with a stirrer 23 and a pipewith a static mixer, is also possible. The ozone gas 24 can be addede.g. by being bubbled 25 into the process water 11, at as small gasbubbles as possible, in order to achieve a contact surface with theprocess water 11 that is as large as possible. Mixing-in can tale placeis e.g. by bubbling equipment, e.g. acting from the bottom of acontainer 27 in which the process water 11 is contained. Mixing-in canalso take place via a mixing-in pump such as a type of turbine pump, orby adding ozone gas 24 into a pipe by aid of a so called ejector or by adosing lance. The mixing of the process water 11 and the added ozone gas24 should be as good as possible. If it is desired to recycle parts ofthe bio-sludge 8 that is separated in the external purification 7 (seeFIG. 1), parts of the sludge 8 can be recycled to the container 27 inwhich the ozone gas 24 is added to the process water 11.

In the brief description above, the principles for the action of theozone gas are thoroughly discussed.

In the description above, the method has been described when using ozonegas.

Naturally, other oxidizing agents can be used at greater or less extent,and in combination. It is also conceivable that the part of the whitewater 15 from the forming equipment 14, that is recycled directly to thepulp and stock preparer 10, is exposed to an ionization and oxidationstep. Furthermore, water 20 from storage tank 19 can be exposed to anionization and oxidation step in direct connection with the pulp andstock preparer 10.

1-8. (canceled)
 9. A method for rendering the flocculation moreeffective in the production of cellulose-based products, comprising thesteps: a) preparing a pulp and water mixture from raw material, freshwater, and recycled white water from step c); b) ionizing and oxidizingthe pulp and water mixture, wherein the pulp and water mixture producedin step a) is subjected to ozone gas, and wherein the ozone gasfunctions both as an oxidant and as an ionizer chemically affecting thesubstances in the pulp to become more reactive and form largeraggregates rendering the flocculation more effective in the pulp andwater mixture; and c) forming a cellulose-based product from the ionizedand oxidized pulp and producing a white water, and supplying at least apart of the white water to step a) as recycled white water.
 10. A methodaccording to claim 9, further comprising supplying retention agents tothe pulp and water mixture between step a) and step b).
 11. A methodaccording to claim 9, further comprising supplying retention agents tothe pulp and water mixture between step b) and step c).
 12. A methodaccording to claim 9, further comprising at least partially subjectingthe incoming recycled white water of step a) to ozone gas.
 13. A devicerendering the flocculation more effective in the production ofcellulose-based products, comprising: a pulp and stock preparer; formingequipment in communication with the pulp and stock preparer, a pulp andwater mixture line between the pulp and stock preparer and the formingequipment arranged to supply the forming equipment with the pulp andwater mixture from the pulp and stock preparer, at least one recyclingline arranged to recycle white water from the forming equipment to thepulp and stock preparer; and ionization and oxidation equipment arrangedto supply ozone gas to the pulp and water mixture line, where the ozonegas functions both as an oxidant and as an ioniozer chemically affectingthe substances in the pulp and water mixture to becomes more reactivewhich thereby forms larger aggregates rendering the flocculation moreeffective in the pulp and water mixture.
 14. A device according to claim13, further comprising a second ionization and oxidation equipmentarranged to supply ozone gas to the at least one recycling line.
 15. Adevice according to claim 14, wherein the second ionization andoxidation equipment is arranged in close connection to the pulp andstock preparer.
 16. A device according to claim 13, wherein theionization and oxidation equipment comprises a reactor vessel having aninlet arranged to receive a pulp and water mixture, an ozone bubblinginlet arrange to bubble ozone gas in a lower part of the reactor vessel,a mixer arranged to mix the pulp and water mixture, and the ozone gas, afirst outlet for the ionization and oxidation treated pulp and watermixture, and second outlets at the upper part of the reactor vesselarranged to receive any remaining ozone gas.
 17. A device according toclaim 13, wherein the first ionization and oxidation equipment isconnected to the pulp and water mixture line in close connection to theforming equipment.